Rubber compositions containing borate compounds

ABSTRACT

The present invention relates to rubber compositions containing borate compounds of the formulawherein R1 and R2 are independently selected from the group consisting of alkoxy radicals having from 1 to 8 carbon atoms; R3 is selected from the group consisting of alkylene groups having from 1 to 15 carbon atoms and arylene and alkyl substituted arylene groups having from 6 to 10 carbon atoms; X is selected from the group consisting ofand Y is selected from the group consisting ofwhere x is an integer of from 1 to 8.

This application claims benefit of Provisional Application No.60/077,607 filed Mar. 10, 1998.

This is a Divisional of application Ser. No. 09/262,184, filed on Mar.4, 1999, now U.S. Pat. No. 6,111,000.

FIELD OF THE INVENTION

The present invention relates to a borate compound which is useful inrubber compositions and the processing of a rubber compositioncontaining borate compounds.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,057,529 discloses a rubber composition containing acarboxylated cobalt oxy metal complex. Representative metals includeboron. These complex carboxylated cobalt oxy metal compounds may beprepared by reacting a cobalt salt of a carboxylic acid with an alkoxideof boron as described in U.S. Pat. No. 3,296,242.

SUMMARY OF THE INVENTION

The present invention relates to borate compounds

wherein R¹ and R² are independently selected from the group consistingof alkoxy radicals having from 1 to 8 carbon atoms; R³ is selected fromthe group consisting of alkylene groups having from 1 to 15 carbon atomsand arylene and alkyl substituted arylene groups having from 6 to 10carbon atoms; X is selected from the group consisting of

and Y is selected from the group consisting of

S_(x) and Se_(x)

where x is an integer of from 1 to 8.

DETAILED DESCRIPTION OF THE INVENTION

There is also disclosed a method for processing a silica-filled rubbercomposition which comprises mixing

(i) 100 parts by weight of at least one elastomer containing olefinicunsaturation selected from conjugated diene homopolymers and copolymersand from copolymers of at least one conjugated diene and aromatic vinylcompound; and

(ii) 0.05 to 10 phr of a compound of the formulae

wherein R¹ and R² are independently selected from the group consistingof alkoxy radicals having from 1 to 8 carbon atoms; R³ is selected fromthe group consisting of alkylene groups having from 1 to 15 carbon atomsand arylene and alkyl substituted arylene groups having from 6 to 10carbon atoms; X is selected from the group consisting of

and Y is selected from the group consisting of

S_(x) and Se_(x)

where x is an integer of from 1 to 8.

There is also disclosed a rubber composition comprising an elastomercontaining olefinic unsaturation and a compound of the formulae

wherein R¹ and R² are independently selected from the group consistingof alkoxy radicals having from 1 to 8 carbon atoms; R³ is selected fromthe group consisting of alkylene groups having from 1 to 15 carbon atomsand arylene and alkyl substituted arylene groups having from 6 to 10carbon atoms; X is selected from the group consisting of

and Y is selected from the group consisting of

S_(x) and Se_(x)

where x is an integer of from 1 to 8.

The present invention may be used to process rubbers or elastomerscontaining olefinic unsaturation. The phrase “rubber or elastomercontaining olefinic unsaturation” is intended to include both naturalrubber and its various raw and reclaim forms as well as varioussynthetic rubbers. In the description of this invention, the terms“rubber” and “elastomer” may be used interchangeably, unless otherwiseprescribed. The terms “rubber composition”, “compounded rubber” and“rubber compound” are used interchangeably to refer to rubber which hasbeen blended or mixed with various ingredients and materials and suchterms are well known to those having skill in the rubber mixing orrubber compounding art. Representative synthetic polymers are thehomopolymerization products of butadiene and its homologues andderivatives, for example, methylbutadiene, dimethylbutadiene andpentadiene as well as copolymers such as those formed from butadiene orits homologues or derivatives with other unsaturated monomers. Among thelatter are acetylenes, for example, vinyl acetylene; olefins, forexample, isobutylene, which copolymerizes with isoprene to form butylrubber; vinyl compounds, for example, acrylic acid, acrylonitrile (whichpolymerize with butadiene to form NBR), methacrylic acid and styrene,the latter compound polymerizing with butadiene to form SBR, as well asvinyl esters and various unsaturated aldehydes, ketones and ethers,e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Specificexamples of synthetic rubbers include neoprene (polychloroprene),polybutadiene (including cis -1,4-polybutadiene), polyisoprene(including cis-1,4-polyisoprene), butyl rubber,styrene/isoprene/butadiene rubber, copolymers of 1,3-butadiene orisoprene with monomers such as styrene, acrylonitrile and methylmethacrylate, as well as ethylene/propylene terpolymers, also known asethylene/propylene/diene monomer (EPDM), and in particular,ethylene/propylene/dicyclopentadiene terpolymers. The preferred rubberor elastomers are polybutadiene and SBR.

In one aspect the rubber is preferably of at least two of diene basedrubbers. For example, a combination of two or more rubbers is preferredsuch as cis 1,4-polyisoprene rubber (natural or synthetic, althoughnatural is preferred), 3,4-polyisoprene rubber,styrene/isoprene/butadiene rubber, emulsion and solution polymerizationderived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers andemulsion polymerization prepared butadiene/acrylonitrile copolymers.

In one aspect of this invention, an emulsion polymerization derivedstyrene/butadiene (E-SBR) might be used having a relatively conventionalstyrene content of about 20 to about 28 percent bound styrene or, forsome applications, an E-SBR having a medium to relatively high boundstyrene content, namely, a bound styrene content of about 30 to about 45percent.

The relatively high styrene content of about 30 to about 45 for theE-SBR can be considered beneficial for a purpose of enhancing traction,or skid resistance, of the tire tread. The presence of the E-SBR itselfis considered beneficial for a purpose of enhancing processability ofthe uncured elastomer composition mixture, especially in comparison to autilization of a solution polymerization prepared SBR (S-SBR).

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

Emulsion polymerization prepared styrene/butadiene/acrylonitrilecopolymer rubbers containing about 2 to about 40 weight percent boundacrylonitrile in the copolymer are also contemplated as diene basedrubbers for use in this invention.

The solution polymerization prepared SBR (S-SBR) typically has a boundstyrene content in a range of about 5 to about 50, preferably about 9 toabout 36, percent. The S-SBR can be conveniently prepared, for example,by organo lithium catalyzation in the presence of an organic hydrocarbonsolvent.

A purpose of using S-SBR is for improved tire rolling resistance as aresult of lower hysteresis when it is used in a tire tread composition.

The 3,4-polyisoprene rubber (3,4-PI) is considered beneficial for apurpose of enhancing the tire's traction when it is used in a tire treadcomposition. The 3,4-PI and use thereof is more fully described in U.S.Pat. No. 5,087,668 which is incorporated herein by reference. The Tgrefers to the glass transition temperature which can conveniently bedetermined by a differential scanning calorimeter at a heating rate of10° C. per minute.

The cis 1,4-polybutadiene rubber (BR) is considered to be beneficial fora purpose of enhancing the tire tread's wear, or treadwear. Such BR canbe prepared, for example, by organic solution polymerization of1,3-butadiene. The BR may be conveniently characterized, for example, byhaving at least a 90 percent cis 1,4-content.

The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber arewell known to those having skill in the rubber art.

The term “phr” as used herein, and according to conventional practice,refers to “parts by weight of a respective material per 100 parts byweight of rubber, or elastomer.”

The borate compounds of the present invention are of the formula

wherein R¹ and R² are independently selected from the group consistingof alkoxy radicals having from 1 to 8 carbon atoms; R³ is selected fromthe group consisting of alkylene groups having from 1 to 15 carbon atomsand arylene and alkyl substituted arylene groups having from 6 to 10carbon atoms; X is selected from the group consisting of

and Y is selected from the group consisting of

S_(x) and Se_(x)

where x is an integer of from 1 to 8. Preferably, each R¹ and R² arealkoxy radicals having from 1 to 3 carbon atoms, R³ is an alkylene grouphaving from 1 to 3 carbon atoms, X is S_(x) and Y is —SH. The boratecompounds may comprise a high purity product or mixture of productsconforming to the above formula.

The borate compound of Formula I where X is —SH may be preparedaccording to the reaction scheme listed below.

The borate compound of Formula I where X is —SCN may be preparedaccording to the reaction scheme listed below.

The borate compound of Formula I where X is an epoxide group may beprepared according to the reaction scheme listed below.

The borate compound of Formula I where X is an episulfide may beprepared according to the reaction scheme listed below.

The borate compound of Formula I where X is a vinyl group maybe-prepared according to the reaction scheme listed below.

The borate compound of Formula I where X is an amine may be preparedaccording to the reaction scheme listed below.

The borate compound of Formula II where Y is S_(x) may be preparedaccording to the reaction scheme listed below.

The borate compound of Formula II where Y is Se_(x) may be preparedaccording to the reaction scheme listed below.

The above reactions are generally conducted in the presence of asuitable solvent. The primary criteria is to use a solvent which doesnot react with the starting materials or end product. Representativeorganic solvents include chloroform, dichloromethane, carbontetrachloride, hexane, heptane, cyclohexane, xylene, benzene, toluene,aliphatic and cycloaliphatic alcohols. Preferably, water is avoided toprevent reaction with the siloxy groups of the compounds.

The borate compounds used in the present invention may be added to therubber by any conventional technique such as on a mill or in a Banbury.The amount of the borate compound may vary widely depending on the typeof rubber and other compounds present in the rubber composition.Generally, the amount of the borate compound is used in a range of fromabout 0.05 to about 10.0 phr with a range of 0.1 to about 5.0 phr beingpreferred. The borate compound is preferably added in the nonproductivestage.

For ease in handling, the borate compound may be used per se or may bedeposited on suitable carriers. Examples of carriers which may be usedin the present invention include silica, carbon black, alumina, aluminasilicates, clay, kieselguhr, cellulose, silica gel and calcium silicate.

The rubber composition may contain a sufficient amount of filler (suchas silica, alumina, aluminosilicate and/or carbon black) to contribute areasonably high modulus and high resistance to tear. The filler may beadded in amounts ranging from 10 to 250 phr. More specifically, silicais generally present in an amount ranging from 15 to 80 phr. If carbonblack is also present, the amount of carbon black, if used, may vary.Generally speaking, the amount of carbon black will vary from 0 to 80phr. Preferably, the amount of carbon black will range from 0 to 40 phr.It is to be appreciated that the silica coupler may be used inconjunction with a carbon black, namely pre-mixed with a carbon blackprior to addition to the rubber composition, and such carbon black is tobe included in the aforesaid amount of carbon black for the rubbercomposition formulation.

Where the rubber composition contains both silica and carbon black, theweight ratio of silica to carbon black may vary. For example, the weightratio may be as low as 1:5 to a silica to carbon black weight ratio of30:1. Preferably, the weight ratio of silica to carbon black ranges from1:3 to 5:1. The combined weight of the silica and carbon black, asherein referenced, may be as low as about 30 phr, but is preferably fromabout 45 to about 90 phr.

The commonly employed siliceous pigments used in rubber compoundingapplications can be used as the silica in this invention, includingpyrogenic and precipitated siliceous pigments (silica) andaluminosilicates, although precipitate silicas are preferred. Thesiliceous pigments preferably employed in this invention areprecipitated silicas such as, for example, those obtained by theacidification of a soluble silicate, e.g., sodium silicate.

Such silicas might be characterized, for example, by having a BETsurface area, as measured using nitrogen gas, preferably in the range ofabout 40 to about 600, and more usually in a range of about 50 to about300 square meters per gram. The BET method of measuring surface area isdescribed in the Journal of the American Chemical Society, Volume 60,page 304 (1930).

The silica may also be typically characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, and more usually about 150 to about 300.

Further, the silica, as well as the aforesaid alumina andaluminosilicate may be expected to have a CTAB surface area in a rangeof about 100 to about 220. The CTAB surface area is the external surfacearea as evaluated by cetyl trimethylammonium bromide with a pH of 9. Themethod is described in ASTM D 3849 for set up and evaluation. The CTABsurface area is a well known means for characterization of silica.

Mercury surface area/porosity is the specific surface area determined byMercury porosimetry. For such technique, mercury is penetrated into thepores of the sample after a thermal treatment to remove volatiles.Set-up conditions may be suitably described as using a 100 mg sample;removing volatiles during 2 hours at 105° C. and ambient atmosphericpressure; ambient to 2000 bars pressure measuring range. Such evaluationmay be performed according to the method described in Winslow, Shapiroin ASTM bulletin, p.39 (1959) or according to DIN 66133. For such anevaluation, a CARLO-ERBA Porosimeter 2000 might be used.

The average mercury porosity specific surface area for the silica shouldbe in a range of about 100 to 300 m²/g.

A suitable pore-size distribution for the silica, alumina andaluminosilicate according to such mercury porosity evaluation isconsidered herein to be five percent or less of its pores have adiameter of less than about 10 nm; 60 to 90 percent of its pores have adiameter of about 10 to about 100 nm; 10 to 30 percent of its pores havea diameter of about 100 to about 1000 nm; and 5 to 20 percent of itspores have a diameter of greater than about 1000 nm.

The silica might be expected to have an average ultimate particle size,for example, in the range of 0.01 to 0.05 micron as determined by theelectron microscope, although the silica particles may be even smaller,or possibly larger, in size.

Various commercially available silicas may be considered for use in thisinvention such as, only for example herein, and without limitation,silicas commercially available from PPG Industries under the Hi-Siltrademark with designations 210, 243, etc; silicas available fromRhone-Poulenc, with, for example, designations of Z1165MP and Z165GR andsilicas available from Degussa AG with, for example, designations VN2,VN3, BV3380GR, etc, and silicas available from Huber, for example HuberSil 8745.

Optionally, conventional sulfur containing organosilicon compounds canbe present in the rubber composition. Examples of suitable sulfurcontaining organosilicon compounds are of the formula:

Z-Alk-S_(n)-Alk-Z  III

in which Z is selected from the group consisting of

where R⁴ is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;

R⁵ is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbonatoms;

Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is aninteger of 2 to 8.

Specific examples of sulfur containing organosilicon compounds which maybe used in accordance with the present invention include:3,3′-bis(trimethoxysilylpropyl) disulfide,3,3′-bis(triethoxysilylpropyl) tetrasulfide,3,3′-bis(triethoxysilylpropyl) octasulfide,3,3′-bis(trimethoxysilylpropyl) tetrasulfide,2,2′-bis(triethoxysilylethyl) tetrasulfide,3,3′-bis(trimethoxysilylpropyl) trisulfide,3,3′-bis(triethoxysilylpropyl) trisulfide,3,3′-bis(tributoxysilylpropyl) disulfide,3,3′-bis(trimethoxysilylpropyl) hexasulfide,3,3′-bis(trimethoxysilylpropyl) octasulfide,3,3′-bis(trioctoxysilylpropyl) tetrasulfide,3,3′-bis(trihexoxysilylpropyl) disulfide,3,3′-bis(tri-2″-ethylhexoxysilylpropyl) trisulfide,3,3′-bis(triisooctoxysilylpropyl) tetrasulfide,3,3′-bis(tri-t-butoxysilylpropyl) disulfide, 2,2′-bis(methoxy diethoxysilyl ethyl) tetrasulfide, 2,2′-bis(tripropoxysilylethyl) pentasulfide,3,3′-bis(tricyclonexoxysilylpropyl) tetrasulfide,3,3′-bis(tricyclopentoxysilylpropyl) trisulfide,2,2′-bis(tri-2″-methylcyclohexoxysilylethyl) tetrasulfide,bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl3′-diethoxybutoxy-silylpropyltetrasulfide, 2,2′-bis(dimethylmethoxysilylethyl) disulfide, 2,2′-bis(dimethyl sec.butoxysilylethyl)trisulfide, 3,3′-bis(methyl butylethoxysilylpropyl) tetrasulfide,3,3′-bis(di t-butylmethoxysilylpropyl) tetrasulfide, 2,2′-bis(phenylmethyl methoxysilylethyl) trisulfide, 3,3′-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3′-bis(diphenylcyclohexoxysilylpropyl) disulfide, 3,3′-bis(dimethylethylmercaptosilylpropyl) tetrasulfide, 2,2′-bis(methyldimethoxysilylethyl) trisulfide, 2,2′-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3′-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3′-bis(ethyldi-sec.butoxysilylpropyl) disulfide, 3,3′-bis(propyldiethoxysilylpropyl-) disulfide, 3,3′-bis(butyl dimethoxysilylpropyl)trisulfide, 3,3′-bis(phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenylethoxybutoxysilyl 3′-trimethoxysilylpropyl tetrasulfide,4,4′-bis(trimethoxysilylbutyl) tetrasulfide,6,6′-bis(triethoxysilylhexyl) tetrasulfide,12,12′-bis(triisopropoxysilyl dodecyl) disulfide,18,18′-bis(trimethoxysilyloctadecyl) tetrasulfide,18,18′-bis(tripropoxysilyloctadecenyl) tetrasulfide,4,4′-bis(trimethoxysilyl-buten-2-yl) tetrasulfide,4,4′-bis(trimethoxysilylcyclohexylene) tetrasulfide,5,5′-bis(dimethoxymethylsilylpentyl) trisulfide,3,3′-bis(trimethoxysilyl-2-methylpropyl) tetrasulfide,3,3′-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide.

The preferred sulfur containing organosilicon compounds are the3,3′-bis(trimethoxy or triethoxy silylpropyl) sulfides. The mostpreferred compounds are 3,3′-bis(triethoxysilylpropyl) tetrasulfide and3,3′-bis(triethoxysilylpropyl) disulfide. Preferably Z is

where R⁵ is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms beingparticularly preferred; Alk is a divalent hydrocarbon of 2 to 4 carbonatoms with 3 carbon atoms being particularly preferred; and n is aninteger of from 2 to 4.

The amount of the above sulfur containing organosilicon compound in arubber composition may range from 0.1 to 40 phr. Preferably, the levelof sulfur containing organosilicon compound may range from 5 to 15 phr.When a filler is used, the level of sulfur containing organosiliconcompound may vary depending on the level of filler that is used.Generally speaking, the amount of the compound of formula III will rangefrom 0 to 1.0 parts by weight per part by weight of the filler.Preferably, the amount will range from 0 to 0.4 parts by weight per partby weight of the filler.

In accordance with one aspect of this invention, a rubber composition isprepared by a process which comprises the sequential steps of:

(A) thermomechanically mixing in at least one preparatory mixing step toa temperature of about 140° C. to about 190° C., for a total mixing timeof about 2 to about 20 minutes (i) 100 parts by weight of at least oneelastomer containing olefinic unsaturation selected from conjugateddiene homopolymers and copolymers and copolymers of at least oneconjugated diene and aromatic vinyl compound; (ii) about 10 to about 250phr of particulate filler selected from the group consisting ofprecipitated silica, alumina, aluminosilicate, carbon black and mixturesthereof; (iii) about 0.05 to about 10 phr of at least one boratecompound of the formula I or II;

(B) subsequently blending therewith, in a final thermomechanical mixingstep at a temperature to about 100° C. to about 130° C. for a time ofabout 1 to about 3 minutes, about 0.1 to about 5 phr of elementalsulfur.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Typical amounts of reinforcing type carbon blacks(s), for thisinvention, if used, are herein set forth. Representative examples ofsulfur donors include elemental sulfur (free sulfur), an aminedisulfide, polymeric polysulfide and sulfur olefin adducts. Preferably,the sulfur vulcanizing agent is elemental sulfur. The sulfur vulcanizingagent may be used in an amount ranging from 0.5 to 8 phr, with a rangeof from 1.5 to 6 phr being preferred. Typical amounts of tackifierresins, if used, comprise about 0.5 to about 10 phr, usually about 1 toabout 5 phr. Typical amounts of processing aids comprise about 1 toabout 50 phr. Such processing aids can include, for example, aromatic,naphthenic, and/or paraffinic processing oils. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in the Vanderbilt RubberHandbook (1978), pages 344-346. Typical amounts of antiozonants compriseabout 1 to 5 phr. Typical amounts of fatty acids, if used, which caninclude stearic acid comprise about 0.5 to about 3 phr. Typical amountsof zinc oxide comprise about 2 to about 5 phr. Typical amounts of waxescomprise about 1 to about 5 phr. Often microcrystalline waxes are used.Typical amounts of peptizers comprise about 0.1 to about 1 phr. Typicalpeptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

In one aspect of the present invention, the sulfur vulcanizable rubbercomposition is then sulfur-cured or vulcanized.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, preferably about 0.8 to about 1.5,phr. In another embodiment, combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, such as from about 0.05 to about 3 phr, in order toactivate and to improve the properties of the vulcanizate. Combinationsof these accelerators might be expected to produce a synergistic effecton the final properties and are somewhat better than those produced byuse of either accelerator alone. In addition, delayed actionaccelerators may be used which are not affected by normal processingtemperatures but produce a satisfactory cure at ordinary vulcanizationtemperatures. Vulcanization retarders might also be used. Suitable typesof accelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. Preferably, the primary accelerator is asulfenamide. If a second accelerator is used, the secondary acceleratoris preferably a guanidine, dithiocarbamate or thiuram compound.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example theingredients are typically mixed in at least two stages, namely at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur vulcanizing agents are typically mixed in thefinal stage which is conventionally called the “productive” mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The terms “non-productive” and “productive”mix stages are well known to those having skill in the rubber mixingart.

In further accordance with the invention, the process comprises theadditional step of vulcanizing the prepared rubber composition at atemperature in a range of about 140° C. to about 190° C.

Accordingly, the invention also thereby contemplates a vulcanized rubbercomposition prepared by such process.

In additional accordance with the invention, the process comprises theadditional steps of preparing an assembly of a tire orsulfur-vulcanizable rubber with a tread comprised of the said rubbercomposition prepared according to the process of this invention andvulcanizing the assembly at a temperature in a range of about 140° C. toabout 190° C.

Accordingly, the invention also thereby contemplates a vulcanized tireprepared by such process.

Vulcanization of the rubber composition of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. Preferably, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air or in a salt bath.

Upon vulcanization of the sulfur vulcanized composition, the rubbercomposition of this invention can be used for various purposes. Forexample, the sulfur vulcanized rubber composition may be in the form ofa tire, belt or hose. In case of a tire, it can be used for various tirecomponents. Such tires can be built, shaped, molded and cured by variousmethods which are known and will be readily apparent to those havingskill in such art. Preferably, the rubber composition is used in thetread of a tire. As can be appreciated, the tire may be a passengertire, aircraft tire, truck tire and the like. Preferably, the tire is apassenger tire. The tire may also be a radial or bias, with a radialtire being preferred.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What is claimed is:
 1. A tire characterized by rubber compositioncomprising an elastomer containing olefinic unsaturation and a boratecompound of the formulae

wherein R¹ and R² are independently selected from the group consistingof alkoxy radicals having from 1 to 8 carbon atoms; R³ is selected fromthe group consisting of alkylene groups having from 1 to 15 carbon atomsand arylene and alkyl substituted arylene groups having from 6 to 10carbon atoms; X is selected from the group consisting of

and Y is selected from the group consisting of S_(x) and Se_(x) where xis an integer from 1 to
 8. 2. The tire of claim 1 wherein each R¹ and R²are alkoxy radicals having 1 to 3 carbon atoms and R³ is an alkylenegroup having 1 to 3 carbon atoms.
 3. The tire of claim 1 wherein Y isS_(x).
 4. The tire of claim 1 wherein X is —SH.
 5. The tire of claim 1wherein said borate compound is present in an amount ranging from 0.05to 10.0 phr.
 6. The tire of claim 1 wherein said elastomer containingolefinic unsaturation is selected from the group consisting of naturalrubber, neoprene, polyisoprene, butyl rubber, polybutadiene,styrene-butadiene copolymer, styrene/isoprene/butadiene rubber, methylmethacrylate-butadiene copolymer, isoprene-styrene copolymer, methylmethacrylate-isoprene copolymer, acrylonitrile-isoprene copolymer,acrylonitrile-butadiene copolymer, EPDM and mixtures thereof.
 7. Thetire of claim 1 wherein said composition is in the tread.